I picked “some event or condition relevant to my life” as more or less the closest: it’s a Looney Tunes (mis)spelling of “trickster,” which referred to my then-profession of puzzle editor.
I picked relevant to my life. I walk in a leisurely manner.
My original user name was an album title by a favorite artist that also had relevance to my view of life.
Now it’s my first name.
Back in the days of beta, my brother and I used to play Counter-Strike v. 1.4. A lot.
We were both pretty damn good.
One of our favorite amusements was to join a “clan” server, where the “clan” was a bunch of poseurs that just had clan tags to pretend they were elite. It tickled us both immensely when said “elite clans” had elaborate and precise text macros to coordinate strategy but the players themselves were awful. So we made our own text macros to mock the silliness while pwning them at the same time. Plus at the same time I was living in a college dorm with no heat so I really did have “game gloves”, which were wool gloves with the fingertips cut off.
One of our “routines” ran something like,
“Terrorists rushing B”
“OK, I’m putting on my game glove”
“Terrorists planting at B”
“Glove is on, switching to hat”
“Bomb planted at B”
“Game Hat is ready, going in”
…we used to infuriate the n00b clans so much with our many routines. The idea of a “Game Hat” tickled me so much so that I’ve kept that username on several sites for about a decade now.
Other - while Tengu do appear in fantasy stories, they’re legendary, not strictly fictional, creatures. They’re pretty awesome, but don’t describe me, so much.
My usual username is of my own invention, and much more personal to me.
Mine is a pun between my RL name and a geometric shape. It just kind of came to me out of the blue.
Mine is derived from the nickname for my RL name (Carol = Caz in Australia). Cazzle is just an embellished version.
I made it up for no particular reason. It’s just German for “I am, you are.” It doesn’t have any associations for me, it was just a random passing thought.
You need a “Songs” or “Music” category, methinks.
Mine is the name of my main toon in WoW
Camping nickname from a gang I no longer hang out with. I’d change it, but I’m too lazy and I figure it’s as good as anything else I could come up with.
Yes, I agree. And I should have included science fiction with fantasy. And I should have included TV with movies and plays. Oh well.
Roddy
My favourite home-made Peruvian dish.
A Tom Paine (and to a lesser extent, Citizen Kane) reference. So ‘History’, I guess. It sounded right! 
Other.
I’ve always wanted to own a Lancia Fulvia Zagato, and until that happy day, this will suffice.
The last word of my favorite play, *Cyrano de Bergerac. *And not, as it turns out, the best translation.
A preexisting nickname category would have been nice, too. But I guess the antepenultimate option will have to do. In real life I am a big guy, and my real name starts with a T.
I voted “fiction”. Though Gargantua & Pantagruel is quite fantastical in nature, it surely doesn’t fit under the modern genre “fantasy”.
Shouldn’t there be a “religious, mythological or legendary” category (Tengu and Chronos, for instance, would fit right in there)?
Mine was given to me by a friend about 13 years ago, from back in the days when I hung with a group in a chat room.